Piston and skirt expanding ring therefor



' PiSTON AND SKIRT EXPANDING RING THEREFOR Filed May 16, 1930 I 71 var: 2'07,

7%: Fr PM Patented May 19, 1931 TENT OFFlCE 7 HAROLD F. PHILLIPS, F BELMONT, MASSACHUSETTS Application filed May 16,

This invention relates to pistons for internal combustion engines and to rings for expanding the skirts of the pistons.

A common type of piston is composed of aluminum or an alloy thereof which has the property of expanding under heat to a considerably greater degree than the iron or iron alloy cylinder in which it reciprocates. T'o

permit the engine to run quietly and without in piston slap when the engine is cold, the cold piston is designed to fit the cold cylinder with but-little clearance. Since the piston when hot would expand and bind in the cylinder it is common to slot the piston skirt horizontally to on one, or both sides, opposite the wrist pin bosses and under the piston rings and also to cut a enerally vertical slot in the skirt which extends from the bottom of the piston into one of the horizontal slots, the diameter of 2a the piston at the rings being, generally, less than at the skirt. With this arrangement, the piston is free to expand circumferentially into the vertical slot, when it becomes hot, without increasing its diameter to such an extent as to bind in the cylinder. The aluminum or alloy comprising the pistons, however, has little resilience and, when the piston becomes highly or excessively heated, takes a permanent set and remains in its expanded position. The piston then becomes loose in the cylinder and sets up a piston slap when the engine is subsequently operated under normal and cooler conditions.

It is an object of the present invention to force the piston back to its normal position or configuration, by the use of an improved form of internally located spring, preferably in the form of an open ended resilient ring which bears constantly on the inner face of the piston skirt and acts to overcome any tendency for the metal to set; and to force the skirt yieldingly against the cylinder wall.

Internal piston rings or springs for this general purpose have been proposed heretofore but all have necessitated the develo ment of peculiar forms of pistons to'retam the rings, which have hindered the commercial adoption of a ring for this purpose. For instance, certain designs have provided special internal grooves, or other constructions not essential to the design of the piston, per se, in which the ring is located.

It is a 'further object of this invention to take advantage of the design of pistons now in commercial use and those parts that are essential or desirable in the design, per se, of the piston and provide expansion rings that can be inserted in the majority of common types of pistons and will engage essential parts of the piston by which the rings will he held in place, without the necessity for altering or modifying the construction therefor.

A common type of piston has opposed passages under the wrist pin bosses or webs and over portions or ledges of the skirt; and it is a further object to provide an expansion ring that has parts located in such passages, between the led es and webs, whereby to anchor the ring against deleterious axial displacement and preferably also against rotation in the piston.

A further object is generally to improve the construction of internal expansion rings for pistons.

Fig. 1 is a side elevation of a piston with which the invention is associated.

Fig. 2 is a sectional elevation through the piston of Fig. 1.

Fig. 3 is a sectional detail taken along line 33 of Fig. 1.

Fig. 4 is a section view taken along line H of Fig. 1.

Fig. 5 is a perspective view of the internal expansion ring of the piston of. Fig. 1.

Fig. 6 is a section elevation of a modified fform of piston and the expansion ring there- Fig. 7 is a plan view of the ring of Fig. 6.

Fig. 8 is a view similar to Fig. 6 but illustrating a further modified form of piston.

The piston illustrated in Figs. 1 to 4, in-

elusive, has the flat head 10 and the cylindrical skirt 12 the upper part of which has ring grooves in which the usual external piston, or gas-sealing rings 14 are located. The opposite sides of the skirt have depressions 16 in which the wrist pin bosses 18 are located, which bosses are connected to the skirt at the sides of the depressions by vertical webs 20. The bottoms of the depressions are 1 end the lower portions of the skirt, at the de-.

pressions, are provided with horizontal ledges 22 which are located below the bottom faces of the webs 20 so that there are passages24 through opposite sides of the piston skirt under said ledges 22. I take advantage ofthis construction in my invention. The skirt is provided with opposite horizontal slots 26 immediately under the piston rings and above the bosses 18 and through the sides opposite said bosses. The skirt also has a generally vertical slot 28, which maybe somewhat inclined, as illustrated, and which extends from the bottom edge of the skirt into one ofsaid horizontal grooves 26. By this construction, the skirt can expand circuinferentially into the slot 28 under heat without undue enlargement of its external diameter. However, as stated above, the skirt does not always return to its original position after it has been highly heated and, in accordance with this invention, I provide an internal rin 30 which isconcentric with the piston and ears on the inner. face of the skirt and forces it outwardly so that it is constrained to return to its original configuration as its cools.

Said ring 30 is preferably of square, al-

though it can be of other substantial crosssection, and it is composed preferably of tempered steel and has a considerable degree of resistance to deformation so that it is highly resilient. It has two opposed circular portions 32 and 34 which fit snugly within opposed portions of the piston skirt under the slots 26 and immediately under the bosses 18 and bear outwardly upon the skirt with considerable pressure. The ring has confronting ends which are located in oneof said portions and on opposite sides of the vertical slot 28. The ring also is formed with other opposed circularportions 36 and 38 which are at right angles to the portions 32 and 34, and are struck from a longer radius and are locatedin the passages 24 under and in engagement with the webs 20 and over and in engagement with the shoulders or ledges 22 of the skirts. The ring is thus held against displacement axially of the cylinder and also is held against rotation so that the ends of the ring are positively located on opposite sides of the slot 28 where they are most effective in forcing the skirt outwardly. The circular portions 36 and 38 are inset within the diameter of the skirt so that they cannot come in contact with, andscore, the cylinder wall. I

In the modification illustrated in Fig. 6, the piston, is provided with an internal annular shoulder 40 which isclose to and, in some instances, merges into the opposed pas-- sages 24 so that the ring may be caused to be seated partly over the shoulder. In order to seat the ring firmly on the inner face of the piston the inner circular portions 32a and 34a are depressed below the outer portions 36a and 38a so that they can be seated on the piston'under said shoulder 40. I

In the modification illustrated'in Fig. 8, the piston is provided with an inwardly directed annular flange or ledge 42 and the webs 20a that su port the wrist pin bosses 18a have incline sections 44 that connect them with that portion of the skirt beneath the bosses. In this instance the'piston lacks the passages 24. Advantage is taken of this construction in providing an internal expansion ring 46 which is wide, or is of large axial extent, as compared with the previously described rings and is located above said flange or ledge 42 and under the sections 44 v and engages both' and so is held positively against axial displacement. In this instance the ring has no means that cooperates with an essential part of the piston in retaining the ring against rotary movement; and it is which are necessary or desirable for good.

strength, uniform expansion, and the like, are utilized to support the ring within the piston and to ,hold it against displacement.

In addition to retaining the piston skirt to its original diametrical dimensions'when t cools after being excessively heated, the ring also has the advantage of expanding the piston to some degree as wear occurs and thereby compensating for such wear.

I claim:

considered that ,none is needed as there is a I 1. A piston having a slotted skirt, wrist I pin bosses, and other parts essential to the construction thereof, in combination with an expansion ring which is located concentrically within the piston at the skirt thereof and has opposed sections that bear outwardly upon the inner face of and hold said skirt resiliently expanded and other opposed sections that lie between and project circumferentially beyond said first opposed sections and which engage on the top and bottom sides thereof parts of the piston that constitute abutments by which said ring is retained in position against displacement axially of the piston.

2 A piston havinga slotted skirt, wri'st pin bosses, and other parts essential to the construction thereof,-in combination with an expansion ring which is located concentrically within-and has opposed sections that bear outwardly upon the inner face of and hold said skirt resiliently expanded and other opposed sections that lie between and project circumferentially beyond said first opposed sections and which engage on the top and bottom sides thereof parts of the piston that constitute abutments by which saidring is retained in position against displacement axially of the piston and also against rotation within the piston.

3. A piston havin a slotted skirt, wrist in bosses, and we s which connect said sses and skirt, in combination with an ex.- pansion ring which is located concentrically within said skirt and engages the inner face of and resiliently holds said skirt expanded, said ring having engagement at one side with said webs and on the opposite side with a ledge of said skirt whereby said ring is held against displacement axially of the piston.

4. A piston having a slotted skirt, wrist pin bosses, and webs which connect said bosses and skirt, in combination with an expansion ring which is located concentrically within said skirt and engages the inner face of and resiliently holds said skirt expanded, said ring having engagement at one side with said webs and on the opposite side with a ledge of said skirt whereby said ring is held against displacement axially of the piston, said ring also having engagement with another part of said skirt by which it is held against rotation.

5. A piston having a slotted skirt, wrist pin bosses, said skirt having opposed recesses which are open to the interior of the piston, in combination with an expansion ring which is located concentrically within said skirt and bears outwardly on the skirt beyond said recesses and resiliently holds said skirt ex panded and which has opposed parts which are located in said opposed recesses.

6. A piston having a slotted skirt, wrist pin bosses, and opposed passages which extend through said skirt, in combination with an expansion ring which is located concentrically within said skirt and bears outwardly on and resiliently holds said skirt expanded and which has opposed parts which are located in said opposed passages and which engage axially opposed parts of said piston by which the ring is held against displacement axially of the piston.

7. A piston having a slotted skirt, wrist pin bosses, and opposed passages which extend through said skirt, in combination with an expansion rin which is located concentrically within said skirt and bears outwardly on and resiliently holds said skirt expanded and which has opposed parts which are located in said opposed passages and which engage axially opposed parts of said piston by which the ring is held against displacement axially of the piston, said-ring being located between axially opposed parts of sald piston by which the ring 1s held agalnst displacement axially of the piston.

8. A piston having a slotted skirt, wrist pin bosses, and opposed passages which extend through said skirt .under said bosses, in combination with an expansion ring which is located concentrically within and bears outwardly on said skirt and which has op osed parts which are located in said oppose passages.

9. A piston having a slotted skirt, wrist pin bosses, and opposed passages which extend through said skirt under said bosses, in combination with an expansion ring which is located concentrically within and bears outwardly on said skirt and which has opposed parts which are located in said opposed passages and are seated on ledges of said skirt at said passages and engage parts of said bosses whereby the ring is held against displacement in both directions axially of the piston.

10. A piston having a slotted skirt and opposed passages therethrough and wrist pin bosses having websv which are located above said passages and connect said bosses and skirt, in combination with an expansion ring which is located concentrically within and bears outwardly on said skirt and has opposed parts which are located in said passages and at the top engage the lower faces of said webs and at the bottom are seated on ledges of said skirt whereby the ring is held against displacement in both directions axially of the piston.

11. A piston having a slotted skirt and opposed passages therethrough and wrist pin bosses having webs which are located above said passages and connect said bosses and skirt, in combination with an expansion ring which is located concentrically within and bears outwardly on said skirt and has opposed parts which are located in said passages and at the top engage the lower faces of said webs and at the bottom are seated on ledges of said skirt whereby the ring is held against displacement in both directions axially of the piston, said opposed parts also engaging the opposite sides of said passages by which the ring is held against rotation.

12. A piston having a slotted skirt, wrist pin bosses, and opposed passages which extend through said skirt, in combination with an expansion ring which is located concentrically within said skirt and bears outwardopposed parts that are seated on the inner face of the skirt below said ledge and urge said skirt outwardly. p

14. A piston having a skirt, wrist pin bosses and opposed passages in said skirt under said wrist pin bosses,.and an ex ansion ring which has parts located in sai passages and retained against axial displacement by engagement with the upper and lower sides of, said passages andjother parts whichbear outwardly on the inner face of said skirt beyond said passages.

15. A piston having a slotted skirt, oposed wrist pin bosses, webs that connect said osses with said skirt; said skirt having opposed passages therethrough under said-webs,

in combination with an expansion ring which has opposed circular parts located in said'passages and engaged on opposite sides by said skirt and said webs by which the ring is held against displacement axially of the piston and having intermediate parts of lesser diameter which engage and. press outwardly I I onthe inner face of said skirt.

16. An internal expansion ring for pistons having opposed circular ring-locking parts, and intermediate circular piston-expanding parts of lesser diameter.

17. An internal expansion ring for pistons having opposed circular rin docking parts, and intermediate circular piston-expanding parts of lesser diameter, the ring having confronting ends which are located in one of said intermediate parts.

18. ,An internal expansion ringfor pistons having opposed circular ring-locking parts, and intermediate circular plston-expanding parts of lesser diameter which are offset from the plane of said opposed parts.

' 19. An internal expansion ring for pistons having opposed circular ring-locking parts and intermediate circular piston-expanding parts of lesser diameter which are offset from theplane of said opposed parts, the ring havingconfronting ends which are located in one of said intermediate parts.

( In testimony-whereof, I have signed my name to this specification.

HAROLD F. PHILLIPS. 

